Alstar 0.5X Reducer for Photography and Observing - 1.25" Filter Thread (28.5x0.75MM) on Both Sides - Reduces The Focal Length for Visual and Photographic Use
Intended for use with with longer-focal-ratio telescopes and eyepieces of narrow to moderately-wide apparent fields of view.
Free light transmission - 22.5mm lens aperture. Can be used with additional spacers (available separately) to achieve further focal reduction.
Mounting threads - 1.25" filter thread (28.5x0.75MM) on both sides: Threads into eyepieces, camera adapters, and other accessories with standard 1.25" threads, and can be stacked with additional 1.25" threaded accessories.
2 lenses for better correction - cemented together and coated, black-anodized aluminum housing. eces: Expand your telescope accessories with this cased 2" eyepiece set (40mm, 32mm and 26mm in focal length) and use it to get into the fascinating world of deep sky observing. The larger lenses mean you get a much larger field of view than with 1.25" eyepieces of the same focal length. The generous eye relief also means that they are very comfortable to use - even when wearing glasses.
85mm focal length, reduction factor of about 0.5X, depending on spacing. 0.5x focal reducer effectively halves the focal length of a telescope, enabling lower magnification, a wider field of view, and shorter exposure times for astrophotography.
